The field of the invention relates generally to methods and systems for trace detection, and more particularly, to integrated vapor and particulate sampling.
Some known trace detection apparatus use two distinct sampling systems, one optimized for vapor sampling and another separate system used for particulate sampling. Such trace detection apparatus either collect samples of analyte by physically removing microscopic particles from surfaces or by collecting and concentrating vapors from the air.
Within such trace detection apparatus, microscopic particles of explosives, drugs or other compounds of interest are removed or harvested by using a sampling device, such as for example a cloth, paper strip, swab or other particle-trapping device. The sampling device is wiped over a surface of interest, then placed into a desorption device which is in communication to a trace chemical detector, such as an ion mobility spectrometer. The sampling device and trapped particles are heated in the desorption device (desorber) to the point where such particles are vaporized. The vapor generated in the desorber is channel to the chemical detection system for analysis.
Explosive vapors, chemicals weapon agents, toxic industrial compounds, illicit drugs and other targeted compounds such as hydrocarbons can also be detected by sensing vapors emitted from the substance. In some known vapor sampling systems, a volume of air is typically collected onto a pre-concentrator. A pre-concentrator adsorbs target molecules from air flowing at a high rate and relatively large volume, allowing molecules from substances not of interest to pass through to an exhaust line. The adsorbing medium is flash heated to vaporize the analyte into a low volume and channeled continuously via a desorbtion airflow, which is directed into a detector such as an ion mobility spectrometer. This process allows the target molecules present in the large air volume initially sampled into the preconcentrator to be concentrated into a much smaller air volume greatly increasing the concentration.
However, analyzing particulate or vapor presents requires a user to physically remove one sampling system, connect the other and recalibrate the apparatus. Moreover, many such systems require different operating temperatures for vapor and particle analysis. Changing temperatures from particle to vapor detection mode requires time to allow the detector temperature to stabilize and may require a system recalibration. Furthermore, after vapor collection, pre-concentrators may be heated quickly to a single, high-temperature set point to volatilize the collected compounds. This may result in the thermal decomposition of some targeted substances.